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Biomedical subjects

S C Chang

Publications and source records attributed to S C Chang.

At least 271 records · Page 15Linked to original sources
PubMed1991

In vitro activities of 36 antimicrobial agents against clinically isolated Bacteroides fragilis.

Thirty-six antimicrobial agents were evaluated for in vitro activities against 100 clinical isolates of Bacteroides fragilis. The minimal inhibitory concentration (MIC) of each agent for each isolate was determined by the agar dilution method. Among 25 beta-lactam antibiotics, the most active agent was imipenem with an MIC90 and a geometric mean of 1 and 0.15 micrograms/ml, respectively; followed by ticarcillin-clavulanic acid, and amoxicillin-clavulanic acid. Ampicillin-sulbactam, piperacillin-tazobactam, moxalactam, and flomoxef were the next most active agents. Piperacillin, ticarcillin, ceftizoxime, cefotaxime, cefuzonam, cefoxitin, and cefmetazole were equally active with the MIC50s ranging from 4 to 16 micrograms/ml, and MIC90s ranging from 32 to greater than or equal to 256 micrograms/ml. The remaining 10 beta-lactam antibiotics, ampicillin, amoxicillin, cefazolin, cefuroxime, cefoperazone, cefmenoxime, ceftazidime, cefpirome, aztreonam, and carumonam were less active. All isolates were resistant to cefotiam at a low breakpoint. Among 6 quinolones, ciprofloxacin was the most active agent with an MIC50 and an MIC90 of 4 and 16 micrograms/ml, respectively. All isolates were resistant to nalidixic acid, pipemidic acid, cinoxacin, enoxacin, and norfloxacin. Among 5 frequently used agents, chloramphenicol, ornidazole, and metronidazole were the most effective agents which inhibited 100% of the isolates at 8, 2, and 2 micrograms/ml, respectively; while clindamycin and minocycline had less activity.

4-Quinolones↗
PubMed1991

Antimicrobial activities of piperacillin alone and in combination with tazobactam against beta-lactamase-producing bacteria.

Tazobactam (YTR 830), a new beta-lactamase inhibitor, was evaluated for its effect in combination with piperacillin, a broad spectrum, but beta-lactamase sensitive, penicillin, against 14 common bacteria. A total of 1,086 clinical isolates from different clinical specimens were tested for beta-lactamase production by the rapid chromogenic cephalosporin method. Their susceptibilities to piperacillin alone and in combination with tazobactam in a ratio of 8:1 by the agar dilution method were evaluated. The percentage of beta-lactamase producing strains ranged from 14.5% to 100% in these tested species. In general, the beta-lactamase producers were more resistant to piperacillin than the beta-lactamase nonproducers with higher minimal inhibitory concentrations (MICs). For the beta-lactamase producers, tazobactam decreased the MICs of piperacillin prominently in methicillin-resistant Staphylococcus aureus, Neisseria gonorrhoeae, Haemophilus influenzae, Escherichia coli, Proteus mirabilis, Morganella morganii, Salmonella species and Bacteroides fragilis, with a 4-fold or greater decrease in MIC50, MIC90 and the geometric mean of MIC. For Serratia marcescens and Pseudomonas aeruginosa, the MICs did not change after adding tazobactam. For other species, there was a moderate decrease in MICs. We conclude that tazobactam is an effective beta-lactamase inhibitor for increasing the antimicrobial activity of piperacillin against beta-lactamase producing strains of many species of bacteria.

Ampicillin Resistance↗
PubMed1991

Acinetobacter calcoaceticus bacteremia: analysis of 48 cases.

The medical records of 48 patients with Acinetobacter calcoaceticus bacteremia over a recent two-year period were reviewed retrospectively to determine the epidemiologic and clinical features. There were 34 males and 14 females with a median age of 51 years. Forty-six of the cases were hospital-acquired. The characteristics of these patients included residence in the intensive care unit, intubation and ventilatory support, preceding antibiotic therapy and intravascular catheterization. In vitro susceptibility testing for the isolated organisms revealed that 32% of these strains were resistant to gentamicin and 90% were aztreonam-resistant. Minocycline, amikacin, ceftazidime, ticarcillin, imipenem, and the new quinolones retained good activity. Although A. calcoaceticus causes septic pictures as do other aerobic Gram-negative bacilli and part of these isolates are multiple drug-resistant, the infection did not seem to be difficult to control. Twenty-six (54%) of these patients survived, including 9 patients without appropriate antimicrobial therapy initiated within 48 hours of blood sampling. The mortality was rarely due to bacteremia per se; most often, it resulted from the underlying diseases.

Acinetobacter Infections↗
PubMed1991

Actinobacillus actinomycetemcomitans endocarditis: a report of four cases and review of the literature.

Four patients with infective endocarditis caused by Actinobacillus actinomycetemcomitans seen at the National Taiwan University Hospital between January 1985 and December 1990 are reported. There were two men and two women with a mean age of 40 years. Three had had a xenograft replacement, the other one had prolapse of mitral valve. Carious teeth were noted in two. The most common presenting symptoms were fever, cough, dyspnoea, and weight loss and the duration of symptoms before diagnosis varied from 2 weeks to 2 months. Peripheral stigmata of endocarditis were not present in any patient. Laboratory investigation revealed haematuria and anaemia in three patients, and elevated erythrocyte sedimentation rates in all four. None had leucocytosis. Echocardiography was performed more than once for each patient and vegetation was demonstrated in only one. Blood culture became positive after 7-10 days of incubation. One of the isolates was resistant to penicillin. The diagnosis was delayed due to the indolent clinical course, non-specific presentation, and the slow growth of the organism. However, all patients were cured clinically and bacteriologically after 6 weeks of intravenous antibiotic therapy which included penicillin, cefamandole, chloramphenicol, or aztreonam, with or without an aminoglycoside. All patients were free of evidence of recurrence after 6-25 months of follow-up.

Actinobacillus Infections↗
PubMed1991

Antibacterial activities of amoxicillin alone and in combination with clavulanic acid correlated with beta-lactamase production.

Amoxicillin, a beta-lactam antibiotic, was tested for its effect in combination with clavulanic acid, a beta-lactamase inhibitor, against 9 species of bacteria isolated from clinical specimens. A total of 698 strains of bacteria were tested for beta-lactamase production by the rapid chromogenic cephalosporin method. Their susceptibilities to amoxicillin alone and in combination with clavulanic acid were tested by the agar dilution method. The percentage of beta-lactamase producing strains ranged from 46.6% in Proteus mirabilis to 100% in Klebsiella pneumoniac. In general, beta-lactamase nonproducers were more susceptible to amoxicillin than beta-lactamase producers. For beta-lactamase producers, clavulanic acid decreased the MICs of amoxicillin prominently in strains of Neisseria gonorrhoeae, Haemophilus influenzae, Escherichia coli, K. pneumoniae, P. mirabilis, Enterobacter cloacae and Bacteroides fragilis, when combining clavulanic acid with amoxicillin in the ratio of 1:2. Their MIC50s, MIC90s and geometric means of MICs all decreased 4 folds or greater. For beta-lactamase non-producing strains, the MICs did not show significant differences by adding clavulanic acid in most species we tested, including methicillin-sensitive Staphylococcus aureus, N. gonorrhoeae, H. influenzae, Proteus vulgaris and E. cloacae.

Amoxicillin↗
PubMed1991

Potentiation effect of corn extract on the production of eremofortin C, EC oxidase, and PR toxin by Penicillium roqueforti.

Eremofortin C (EC) and PR toxin are secondary metabolites of Penicillium roqueforti. Their structures are similar and differ only by an alcohol and an aldehyde group at the C-12 position. EC has been demonstrated to be the precursor of PR toxin, and EC is transformed to PR toxin by EC oxidase. These two compounds and EC oxidase are secreted by P. roqueforti in the culture medium, which is usually composed of 15% sucrose and 2% yeast extract. Recently, we discovered that the addition of corn extract to this medium increased the production of EC and PR toxin and the activity of EC oxidase in a coordinative manner. In a time-course study, we found that the peak yield of EC and PR toxin and the maximum activity of EC oxidase in the culture medium containing 7.5% sucrose, 1% yeast extract, and 20% corn extract were increased 6.2, 4.6, and 4.7-fold, respectively, as compared with those obtained in the medium without corn extract. Moreover, corn extract increased the production of EC and PR toxin and the activity of EC oxidase by P. roqueforti in a dose-dependent manner. On the other hand, when the concentrations of sucrose and yeast extract were increased while fixing the ratio of corn extract, we found that the levels of EC and PR toxin and the enzyme activity were decreased concomitantly. We thus conclude that corn extract can enhance the production of EC, PR toxin and EC oxidase by P. roqueforti when grown in a minimal medium and that the potentiation effect of corn extract is suppressed when the fungi are grown in a rich medium.

Alcohol Oxidoreductases↗
PubMed1991

The value of roentgenographic and fiberbronchoscopic findings in predicting outcome of adults with lower lung field tuberculosis.

Proper antituberculosis chemotherapy may not prevent occurrence or progression of endobronchial involvement in patients with pulmonary tuberculosis. We previously reported a higher incidence of endobronchial involvement in adults with lower lung field tuberculosis (LLFTB). We evaluated the value of roentgenographic and fiberbronchoscopic findings in predicting the outcome of adults with LLFTB after 9 months of antituberculosis chemotherapy. The most common change on chest roentgenograms among 101 patients with LLFTB was consolidation, followed by cavitary lesion, lung collapse, and solitary mass. Intrathoracic lymphadenopathy (hilar and/or mediastinal lymphadenopathy) was found in 12 cases. Sputum smear for acid-fast bacilli was positive in 64 patients, and sputum culture for tuberculous bacilli was positive in 37 of 50 patients. Endobronchial involvement was found in 45 of 63 patients who underwent fiberbronchoscopic examination. Of these 45, 18 had ulcerative granuloma, 12 had fibrostenosis, eight had submucosal infiltration, and seven had mucosal redness and swelling. A higher incidence of endobronchial involvement was found in the patients with LLFTB when they presented with roentgenographic findings of pulmonary consolidation, lung collapse, or associated intrathoracic lymphadenopathy. The outcome seemed unfavorable in the patients with LLFTB who presented with roentgenographic findings of lung collapse or pulmonary consolidation, or in those who presented with fiberbronchoscopic findings of fibrostenosis or ulcerative granuloma. Our results show that roentgenographic and fiberbronchoscopic findings are of value in predicting outcome of patients with LLFTB. With proper antituberculosis chemotherapy and close follow-up, fiberbronchoscopy may be clinically indicated in patients with LLFTB to assess the presence and severity of endobronchial involvement. Early surgical intervention can be considered in those with severe endobronchial involvement before serious sequelae occur.

Adult↗
PubMed1991

Analysis and tracing of polycyclic aromatic hydrocarbons and mutagenicity of airborne particulates from the Taipei area.

In a 3-year study, we determined the mutagenicity and polycyclic aromatic hydrocarbons (PAHs) of airborne particulates collected during December 1987-September 1988 (216 samples), October 1988-January 1989 (81 samples), and October 1989-April 1990 (52 samples) from 9 locations in the Taipei area. We found that dichloromethane extracts of all the samples were mutagenic to Salmonella typhimurium in the Ames test. Moreover, the mutagenicity was much higher in the presence of rat liver microsomal fraction (S9 mixture) than that observed in its absence, which indicates that airborne particulates contained both direct and indirect mutagens. The average mutagenicity of the samples collected in the 3-year period was 137, 127, and 118 histidine revertants/10 m3 air, respectively. On the other hand, we found that dichloromethane extracts of each airborne particulate sample contained 14 PAHs with wide variations in concentration and relative distribution. The levels of Pha, Flu, Pyr, and Ben were much higher than the PAHs with higher ring numbers such as BaP, BeP, Pr, IP, and DbA. The average PAH content was 8.0, 5.0, and 7.8 ng/m3 air for airborne particulates collected during December 1986-September 1987, October 1988-January 1989, and October 1989-April 1990, respectively. Among the 9 stations, Fu Hsing Elementary School and Chung Hsing University (Taipei campus), which are, respectively, located in the downtown area and a heavy traffic zone, had significantly higher levels of mutagenicity and PAHs than did the other stations. Moreover, comparative analysis of PAH levels of airborne particulates over the 3-year period revealed an interesting season-dependent change of PAH content in airborne particulates from the Taipei area. The concentrations of individual and total PAHs were consistently lower in the summer than those in the winter. A similar pattern of seasonal change was also observed in the mutagenicity of airborne particulate samples examined. It is worth mentioning that neither PAH level nor mutagenicity of airborne particulates showed significant yearly change over the 3-year period of study. As part of an effort to identify pollution sources, we examined the mutagenicity and PAH compounds of air particulates collected from the burning of garbage (14 samples) and motor-vehicle exhaust in the Hsin Hai Tunnel (17 samples), Taipei. The results showed that garbage burning gave rise to air particulates containing several hundred times higher levels of PAHs and about 20 times stronger mutagenicity, while the motor-vehicle exhaust contained about ten times higher PAH content and mutagenicity as compared with those of airborne particulates of the Taipei city.(ABSTRACT TRUNCATED AT 400 WORDS)

Air Pollutants↗
PubMed1990

(S)-2-hydroxypropyl-beta-cyclodextrin, a new chiral stationary phase for reversed-phase liquid chromatography.

(S)-2- and (R,S)-2-hydroxypropyl-beta-cyclodextrin have been bonded to silica gel and evaluated as stationary phases for reversed-phase liquid chromatography. Stationary phases also were prepared on two silicas having different pore sizes and surface areas. Dissimilarities were observed in enantiomeric selectivities between these columns and also between these and the native beta-cyclodextrin columns. With the exception of compounds 5 and 10, all other racemates reported here which have been successfully resolved on the new phases are enantiomers which have not been previously reported as separated on the beta-cyclodextrin stationary phase. In some cases, there were also differences in enantioselectivities observed between the (S)- and the (R,S)-hydroxypropyl-beta-cyclodextrin phases on the same silica. The results are discussed in terms of the retention mechanism and compared to results reported earlier for beta-cyclodextrin columns.

Chemical Phenomena↗
PubMed1990

Transrectal sonographic cystourethrography: studies in stress urinary incontinence.

Transrectal ultrasonic sagittal transducer is an excellent modality to image the bladder and urethra in dynamic change. In female patients, we found it is also helpful for the diagnosis of urinary stress incontinence. The posterior urethrovesical (PUV) angle is measured with the transrectal sonoprobe under strain and non-strain conditions. We compared the results of sonographic cystourethrogram with the radiographic chain cystourethrogram. The sonographic cystourethrography is superior to the radiography. The former may estimate the PUV angle accurately and differentiate between the patients with and without stress urinary incontinence. Furthermore, we also use the transrectal sagittal probe intraoperatively to adjust the suspension force as well as PUV angle in patients who underwent vesical neck suspension for stress urinary incontinence (SUI).

Adult↗
PubMed1990

The effect of cyclosporine on expression of class II major histocompatibility complex antigens on bronchoalveolar cells and peripheral blood mononuclear cells.

To evaluate the effect of cyclosporine (CsA) on the expression of class II major histocompatibility complex (MHC) antigens on bronchoalveolar cells (BAC) and peripheral blood mononuclear cells (PBMC), BAC and PBMC were obtained from mongrel dogs before and during CsA treatment. Expression of MHC class II antigens on BAC and PBMC were detected by monoclonal antibodies (Mabs) B1F6, 7.5.10.1 and Q5/13, which recognized canine MHC class II antigens, using cytofluorometry. Total cell counts and cell differentials of canine BAC showed no significant difference before or during CsA treatment (P greater than 0.05). Anti-MHC class II Mabs used in this study reacted with 21-51% of canine BAC and with 31-69% of PBMC. After stimulation with phytohaemagglutinin (PHA) the percentages of MHC class II positive BAC and PBMC were significantly increased (P less than 0.001). Whole blood levels of CsA were 315 +/- 76 (mean +/- SD) ng/ml and 343 +/- 57 ng/ml on days 7 and 14 during CsA treatment at an oral dose of 20 mg/kg/day. During CsA treatment there was no significant difference in the percentages of MHC class II positive BAC and PBMC compared with data obtained before CsA treatment (P greater than 0.05). We likewise failed to observe a suppressive effect of CsA on the increased expression of MHC class II antigens on BAC and PBMC induced by PHA (P greater than 0.05). In summary, at an oral dose of 20 mg/kg/day for a period of two weeks, our results show that: (1) CsA does not affect the total cell counts and cell differentials of canine BAC; (2) CsA does not reduce the basal expression of MHC class II antigens on canine BAC and PBMC; (3) CsA does not suppress the increased expression of MHC class II antigens on canine BAC and PBMC induced by PHA.

Animals↗
PubMed1990

MHC class II antigens on canine bronchoalveolar cells.

To evaluate the expression of MHC (major histocompatibility complex) antigens on canine bronchoalveolar cells (BAC), bronchoalveolar lavages (BAL) were performed in mongrel and German shepherd dogs. MHC class II antigens on canine BAC and peripheral blood mononuclear cells (PBMC) were detected by monoclonal antibodies (mAbs) B1F6, 7.5.10.1 and Q5/13 recognising canine MHC class II antigens, using cytofluorometry. These mAbs reacted with more than 20% of BAC and PBMC in both breeds of dog. The percentage of MHC class II positive cells in BAC were lower than those in PBMC. There was no significant difference in the percentages of MHC class II positive BAC and PBMC in mongrel and German shepherd dogs. To further identify the expression of MHC class II antigens on BAC, the cells were separated into adherent and nonadherent cells by petri dish adherence. The percentages of MHC class II positive cells in adherent and non-adherent cell populations were similar. Nearly half the lymphocytes in normal BAC were T cells detected by mAbs F3-20-7 and 1A1; B cells were scarce and represented less than 10% of nonadherent cells. Immunoprecipitation by anti-MHC class II mAbs, and SDS-polyacrylamide gel electrophoresis (SDS-PAGE) revealed MHC class II-like molecules on canine BAC and PBMC. After stimulation with phytohaemagglutinin (PHA), the percentages of class II positive cells in BAC and PBMC were significantly increased. Thus, these anti-MHC class II mAbs may prove to be of advantage in experiments designed to evaluate the changes in class II antigen expression on canine BAC during the course of immune response in the lung, as in pulmonary allograft rejection.

Animals↗
PubMed1990

Effects of dietary manganese deficiency on rat pancreatic amylase mRNA levels.

Manganese deficiency is associated with increased pancreatic amylase activity in rats. The present study investigated whether this increase in amylase activity is associated with increased pancreatic amylase messenger RNA (mRNA) levels. Weanling rats were fed a high carbohydrate diet containing either 40 micrograms Mn/g (control) or 0.5 microgram Mn/g (deficient) for 4 to 8 wk. Mn deficiency was confirmed by determining hepatic Mn content, which was significantly lower in Mn-deficient rats than in controls. Pancreatic RNA from both groups of rats was hybridized with 32P-labeled complementary DNAs for amylase and trypsinogen. Amylase mRNA levels were increased in rats fed Mn-deficient diets for both 4 wk (200%) and 8 wk (250%) when compared with respective control levels. In contrast, Mn deficiency was not associated with alterations in trypsinogen mRNA levels. Serum levels of insulin and corticosterone, hormones known to increase pancreatic amylase mRNA, were not affected by Mn deficiency. These observations suggest that Mn may participate in the regulation of amylase gene expression in a manner that is independent of insulin and corticosterone.

Administration, Oral↗
PubMed1990

Increased expression of MHC class II antigens in rejecting canine lung allografts.

Expression of major histocompatibility complex class II antigens was investigated in the normal lungs and in lung allografts of mongrel dogs after single-lung transplantation. Cryostat sections were stained with an indirect immunoperoxidase technique that used B1F6 and 7.5.10.1 as anti-MHC class II monoclonal antibodies. In the normal lungs and native lungs of the recipient dogs after single-lung transplantation, only some cells of lymphoid tissue and macrophages/dendritic cells were MHC class II-positive. During acute rejection, increased infiltration with MHC class II-positive cells in perivascular, peribronchial, and interstitial areas and intraalveolar spaces was found in lung allografts. In addition, expression of MHC class II antigens was induced on the bronchial epithelium and vascular endothelium. Induced expression of MHC class II antigens on the bronchial epithelium and vascular endothelium in rejecting lung allografts was found as early as two days after single-lung transplantation. The intensity of MHC class II antigen expression on bronchial epithelium and vascular endothelium in graft lungs increased with the progression of rejection response and directly correlated with the bronchoalveolar lavage fluid (BALF) levels of biochemical markers, as tumor necrosis factor alpha, gamma-interferon (IFN-gamma), interleukin 2 (IL-2) and soluble interleukin 2 receptor (SIL-2R). Abnormal expression of MHC class II antigens on bronchial epithelium and vascular endothelium and abnormal elevation of BALF levels of the cytokines in lung allografts could be prevented by cyclosporine (CsA) treatment. Our results suggested that MHC class II antigen expression could be induced on the bronchial epithelium and vascular endothelium of canine lung allografts during acute rejection. This abnormal expression of MHC class II antigens on bronchial epithelium and vascular endothelium of graft lungs may serve as a specific index for diagnosis of lung allograft rejection when infection as an inducing factor can be excluded. Furthermore, bronchial epithelium and vascular endothelium of lung allografts have become MHC class II-positive, and are likely to be the targets for low-grade rejection, resulting in the development of bronchiolitis obliterans and occlusive vascular disease in lung allografts.

Animals↗
PubMed1990

Pneumothorax following cytotoxic chemotherapy in malignant lymphoma.

Pneumothorax occurring as a complication of the antitumor effect of cytotoxic chemotherapy has been reported in occasional cases of a variety of tumors. Its occurrence in malignant lymphoma has not been reported heretofore. In this report, we describe two cases of this complication in patients with malignant lymphoma and discuss the possible pathophysiologic mechanisms involved. Because pulmonary involvement with the tumor was found in both cases, pneumothorax could be attributed to the anti-tumor effect of cytotoxic agents on underlying lung involvement in patients with malignant lymphoma.

Adult↗
PubMed1990

Antimicrobial activities of six new oral cephem antibiotics.

Six newly developed oral cephem antibiotics, which included 5 with an aminothiazolyl side chain, viz., cefixime, cefotiam hexetil, cefpodoxime proxetil, cefteram pivoxil, ceftibuten, and one with a conventional side chain design, BMY 28100, were tested for their antimicrobial activities. Three traditional oral beta-lactam antibiotics, ampicillin, cephalexin, and cefaclor, were used as reference antibiotics. The 5 aminothiazolyl cephems were more active than the reference drugs against clinical isolates of Escherichia coli, Klebsiella pneumoniae and Haemophilus influenzae. All 6 new drugs showed poor activity against clinical isolates of Enterobacter cloacae, Pseudomonas aeruginosa, and enterococci. They were better than cephalexin and cefaclor, but slightly poorer than or the same as ampicillin in activities against Streptococcus pyogenes and Streptococcus pneumoniae. Cefotiam hexetil, BMY 28100, and cefpodoxime proxetil were also more active than cephalexin against Staphylococcus aureus. Although the 6 tested new oral cephems demonstrated little difference in their activities against different bacteria, they all showed greater antimicrobial activity than the traditional oral antibiotics now in clinical use.

Administration, Oral↗
PubMed1990

Staphylococcus aureus endocarditis in drug addicts: report of 2 cases.

Two young men presented with prolonged hectic fever and chills followed by chest pain, dyspnea and hemoptysis. The chest films revealed multiple lung infiltrates, and blood cultures yielded Staphylococcus aureus. Echocardiographic examination confirmed the diagnosis of tricuspid valve endocarditis. Multiple punctate lesions in the bilateral inguinal areas and dragon tattoos over the forechest gave rise to the suspicion of drug abuse. After prolonged antimicrobial therapy, bacteremia was eliminated, and elective vegetectomy and valvuloplasty were performed on one of the patients. The other one suffered recurrent episodes of pulmonary embolism. Disappearance of the large vegetation was disclosed by echocardiography. Both of them eventually regained their health with the abstinence of drugs. This report illustrates two typical cases of infective endocarditis in drug addicts.

Adult↗